Tehran University of Medical Sciences Iranian Journal of Microbiology 2008-3289 17 6 2025 12 13 942 953 Hafez Al-Momani Department of Microbiology, Pathology and Forensic Medicine, Faculty of Medicine, The Hashemite University, Zarqa, Jordan Safaa Mashal Department of Microbiology, Pathology and Forensic Medicine, Faculty of Medicine, The Hashemite University, Zarqa, Jordan Hadeel AlGhawrie Department of Infection Control, King Hussein Cancer Center, Amman, Jordan 2023 12 09 2025 10 16 Background and Objectives: The antimicrobial resistance of Pseudomonas aeruginosa bacteria limits the spectrum of effective antibiotics. Considerable focus has been placed on the identification of more contemporary and cost-effective antimicrobial drugs. In this study, the antibacterial properties of a commonly used solvent, dimethyl sulfoxide (DMSO), against P. aeruginosa were investigated. Materials and Methods: The microtiter broth dilution technique was employed to establish the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of DMSO. The solvent’s impact on bacterial growth, biofilm formation and eradication was assessed. A quantitative polymerase chain reaction (qPCR) was carried out to assess the effect of varying DMSO concentrations ranging from 1% to 8% (v/v) on quorum sensing gene expression. Results: All P. aeruginosa strains exhibited a DMSO MIC of 25% v/v and MBC of 50% v/v. DMSO caused significant growth inhibition and suppression of biofilm formation in all P. aeruginosa strains at sub-inhibitory concentrations, i.e. 1%-8% v/v. At these concentrations, the samples showed a reduction in biomass and reduced metabolic activity. These effects were concentration-dependent. A DMSO strength of 8% v/v was associated with a statistically significant downregulation of most of the quorum sensing genes; at a DMSO titer of 1% v/v, this effect was modest with only a few genes being significantly affected. Conclusion: DMSO is a potential therapeutic agent against P. aeruginosa as it has been demonstrated that it exhibits antimicrobial characteristics. Moreover, the impact of DMSO on bacterial growth and biofilm formation complicates its use as a solvent in biologic and clinical research. https://ijm.tums.ac.ir/index.php/ijm/article/view/4510 https://ijm.tums.ac.ir/index.php/ijm/article/download/4510/1841